Almost all command error messagesare not translated. The jsons of them use key "text" instead of "translate" and "with".

You can set your game name a languages which is not English, then run a command. When it succeeds, it prints translated message. Instead when it fails, it prints untranslated message.

You can use a command block. For example, use a command block and run /kill @e[name="abc"] and use /data to get the LastOutput of it. You will find *

* instead of *

*.